I recently switched my desktop environment from GNOME to Cinnamon. In my terminal, I use tmux and have my prefix key mapped to Ctrl+Space. After the upgrade, Ctrl + Space stopped being captured by tmux.

I tried running xev and get this output when I hit Ctrl+Space:

KeyPress event, serial 37, synthetic NO, window 0x3400001,

root 0x9e, subw 0x0, time 49566192, (609,435), root:(611,505),

state 0x0, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,

XLookupString gives 0 bytes:

XmbLookupString gives 0 bytes:

XFilterEvent returns: False



FocusOut event, serial 37, synthetic NO, window 0x3400001,

mode NotifyGrab, detail NotifyAncestor



FocusIn event, serial 37, synthetic NO, window 0x3400001,

mode NotifyUngrab, detail NotifyAncestor



KeymapNotify event, serial 37, synthetic NO, window 0x0,

keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

       0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

I am running Ubuntu 14.04 (Trusty Tahr), and Cinnamon 2.0.14.